Tetranitromethane (TNM) is a common byproduct resulting from the nitration of many organic substances. TNM is a toxic material. TNM is also an oxidizer that can form a powerful explosive when mixed with combustible organic materials such as benzene, nitrobenzene, toluene, etc. For example, the presence of TNM has been held responsible for explosions in trinitrotoluene manufacturing facilities.
TNM can present other challenges in manufacturing facilities as it is very soluble in strong nitric acid, e.g., greater than about 30% by weight in 99% nitric acid, but not in 40% nitric acid (.about.0.5% by weight) or in 85% sulfuric acid(.about.0.8% by weight). Although TNM is soluble in concentrated nitric acid, it is difficult to separate from concentrated nitric acid.
Moreover, most nitration facilities require recycling of acids, e.g., sulfuric and nitric acids, to provide for an economical and environmentally sound process. The possibility of TNM concentrating in an acid recycle stream is real if a purge or destruction process is not implemented.
The present invention provides a process to safely and effectively remove and destroy TNM from a substantially pure concentrated nitric acid stream without also stripping a significant amount of the nitric acid desired for recycle.